Power plants come in a variety of different designs and sizes. Larger sized power plants may be used to provide electricity to a large geographic area, whereas relatively small power plants may be used to power local areas or manufacturing facilities. In addition to providing electricity, power plants may be used for a myriad of additional or different purposes, from desalinating sea water to creating nuclear isotopes for medical purposes. Similarly, the types of power plants that are available cover a wide spectrum of technologies including gas powered, coal fired, and various types of nuclear power, to name a few.
One common feature between many of these power plants is the production of energy in the form of heat. The heat that is produced may ultimately be used to convert water into steam. When the production of electricity is the desired goal, the steam may be used to run a turbine. Regardless of the source of the heat, a heat transfer system may be used to transfer the heat generated by the power plant to the water that may then be converted to steam. A heat exchanger comprising a number of tubes may be used to exchange the heat between a primary coolant circulating through a reactor core and a secondary coolant that is converted into the steam. In some systems, the same coolant that is heated by the reactor core may be circulated through the tubes.
The tubes may be friction or pressure-fit to a tube sheet by roll-expanding a portion of the tubes within the tube sheet using a mechanical, pneumatic, or hydraulic device to provide a leak tight joint. The tubes may also be welded to the tube sheet. For tubes with secondary coolant boiling inside of the tubes, orifice or flow restriction devices may be provided at the secondary coolant (feedwater) inlet in order to attain secondary flow stability. The orifice device may be welded to the end of the tubes, such as at the inlet. Welded mounting techniques may make it difficult to inspect the tubes after installation. Additionally, one or more of the large number of orifice devices of the heat transfer system may become misaligned during installation, maintenance, inspection and/or operation of the power plant, resulting in an impediment to the flow of coolant through the tubes, an unacceptable amount of bypass leakage, pressure drop, and/or other alignment complications.
The present application addresses these and other problems.